24 Free Precision Solar Tools

Free Solar Calculator Hub
Size, Save & Go Solar with Confidence

Every solar calculator built for US homeowners, DIYers, and off-grid enthusiasts. Panel counts, ROI payback, 30% federal tax credit, off-grid systems, RV solar — all in one place. No sign-up. No cost.

How Many Panels? ROI Payback 30% Tax Credit Off-Grid System RV Solar Peak Sun Hours
24+
Solar Calculators
30%
ITC Tax Credit Covered
0$
Always Free
IRS 30% ITC CoveredFederal tax credit math built in
NREL Data Backed54 US cities, real insolation data
Off-Grid to Grid-TiedEvery solar scenario covered
PDF ExportShare estimates with installers
Updated 2026Current panel prices and rates
Grid-Tied & ROI Battery & Backup Off-Grid & RV Components & Wiring Appliance-Specific Sun & Location

Which Solar Calculator Do You Need? Quick Reference Guide

Your SituationStart With This ToolThen Use These
Homeowner evaluating rooftop solarHow Many Panels?ROI Payback → Federal Tax Credit → Net Metering
Want backup power during outagesHome Battery BackupSolar Battery Bank → Inverter Size
Building a complete off-grid homesteadOff-Grid SystemDays of Autonomy → Well Pump → Charge Controller
Outfitting an RV or vanRV SolarSeries vs Parallel → Wire Size → Inverter Size
Running one specific appliance on solarAC, Fridge, or Well Pump calculator (above)Peak Sun Hours → Charge Controller
Not sure how much sun you getPeak Sun HoursTilt Angle → How Many Panels?
Sizing wiring for an existing systemWire Size GaugeSeries vs Parallel → Charge Controller
24+
Solar Calculators
30%
ITC Tax Credit Built In
54+
US Cities in Sun Database
0$
Always Free
Why These Calculators

Built to Outperform Every Other Solar Calculator Online

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25-Year NPV Included in Every ROI Tool

Most solar ROI calculators give you a simple payback period. Ours gives you net present value over 25 years, factoring in panel degradation at 0.5%/yr, utility rate escalation, and the real value of money over time.

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Full IRS Inflation Reduction Act Math

The 30% federal solar tax credit has specific eligibility rules. Our calculator follows current IRS guidance and also surfaces state-level incentives, battery storage adders, and income phase-out limits.

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Real NREL Insolation Data — Not Averages

We use actual National Renewable Energy Laboratory peak sun hour data for 54 US cities across every climate zone. Phoenix gets 6.5 PSH; Seattle gets 3.8. Your calculator uses the right number for your location.

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Off-Grid Math That DIYers Actually Need

Our off-grid calculators use proper DC-to-AC conversion efficiency (85-90%), NEC 125% safety margins, and depth-of-discharge limits by battery chemistry (AGM vs LiFePO4). No oversimplifications that leave you undersized.

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PDF Export for Installer Quotes

Every major solar calculator includes a branded PDF download. Take your panel count, system specs, and 25-year savings projection to multiple installers. You will negotiate from a position of knowledge, not confusion.

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WhatsApp Share for Fast Estimates

Running numbers on a project for someone else? Hit the WhatsApp share button and send your solar estimate directly. Available on every calculator in this hub.

Common Questions

Frequently Asked Solar Calculator Questions

How many solar panels does the average American home need?+
The average US home uses about 10,500 kWh per year. Divided by average peak sun hours of around 4.5 hours per day, and assuming standard 400W panels at 80% system efficiency, most homes need between 20 and 28 panels. Use our How Many Solar Panels calculator with your actual electric bill for a precise number tailored to your state and utility rate.
What is the 30% federal solar tax credit and do I qualify?+
The 30% Investment Tax Credit under Section 25D of the Inflation Reduction Act allows homeowners to deduct 30% of their total solar system cost from their federal income taxes. This applies to panels, inverters, battery storage, and installation labor. To qualify, you must own (not lease) the system, it must be on your primary or secondary US residence, and you must have sufficient federal tax liability. Our Federal Solar Tax Credit calculator walks through all of these factors.
What are peak sun hours and why do they matter?+
Peak sun hours are not the same as daylight hours. A peak sun hour represents one hour of sunlight at an intensity of 1,000 watts per square meter. Phoenix gets about 6.5 peak sun hours per day. Seattle gets about 3.8. Boston gets about 4.2. This number directly determines how much electricity your solar panels will produce, which affects both your panel count and your financial projections. All of our solar calculators use NREL data to apply the correct peak sun hours for your location.
What size solar system do I need to go completely off-grid?+
Complete off-grid sizing requires calculating your total daily watt-hour consumption, multiplying by your desired autonomy days, and then sizing the battery bank (accounting for depth of discharge limits by battery type) and the solar array to refill that bank on an average peak sun hour day with a 20% margin for system losses. Our Off-Grid Solar System calculator does all four components simultaneously and outputs a complete materials list with specs for panels, batteries, charge controller, and inverter.
What is the difference between MPPT and PWM charge controllers?+
PWM (Pulse Width Modulation) controllers are simpler and cheaper but require your panel voltage to closely match your battery bank voltage. MPPT (Maximum Power Point Tracking) controllers are more efficient, typically 93-97% vs 70-80% for PWM, and can handle panel array voltages much higher than your battery voltage by converting the excess voltage to additional current. For any system above 200 watts, MPPT is almost always the better investment. Our charge controller calculator recommends the right type and amperage for your specific panel and battery configuration.
How long do solar panels actually last?+
Most tier-one solar panels come with a 25-year linear performance warranty guaranteeing at least 80-85% of original power output at year 25. The typical degradation rate is 0.5% per year. Panels do not stop working at 25 years — they continue producing power, just at reduced output. Our ROI calculator models this 0.5%/yr degradation through the full 25-year horizon so your savings projections reflect real-world panel performance rather than day-one output rates.
Can I run an air conditioner on solar power?+
Yes, but AC units are among the most demanding solar loads because of their high starting surge current (often 3-5x running watts) and high continuous draw. A 1-ton (12,000 BTU) mini-split running 8 hours per day needs roughly 1,200-1,500 kWh per month just for cooling. Our Solar Air Conditioner calculator translates your BTU rating into the required solar panel wattage and battery capacity to run it reliably, accounting for starting surge and your local peak sun hours.
What AWG wire size should I use for my solar system?+
Wire size depends on three factors: the current flowing through the wire (amps), the length of the wire run (one-way distance), and the acceptable voltage drop (NEC recommends no more than 3% on DC circuits). For a typical 40-amp charge controller with a 20-foot run, you would need 8 AWG wire minimum, stepping to 6 AWG at 30 feet or 4 AWG at 50 feet. Our Solar Wire Size calculator handles all three variables and outputs the minimum AWG for safe, compliant wiring to NEC 690 solar installation standards.
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Disclaimer & Editorial Transparency: The solar calculators on this page are for estimation and educational purposes only. Solar panel output, payback periods, and savings projections depend on local utility rates, installation quality, roof condition, shading, local permit requirements, and incentive availability that this tool cannot know. Federal tax credit calculations reference current IRS guidance under the Inflation Reduction Act but should be verified with a tax professional. All pricing estimates use US national averages and may not reflect your local market. Always obtain multiple installer quotes before purchasing a solar system. External links to NREL, Energy.gov, and IRS.gov are provided for reference and are governed by those organizations’ own policies.

Start With the Right Solar Calculator

24 free tools built for US homeowners, DIYers, and off-grid enthusiasts. Get your panel count, savings estimate, and federal tax credit in minutes.

How Many Panels Do I Need? Calculate My ROI